The basic elements required for bone formation include a three-dimensional, open-porosity tissue scaffold, cells, and osteoinductive signaling molecules to stimulate cell differentiation, proliferation, and matrix formation. The biologic, physical, and biomechanical properties of the materials, compositions, and constructs are some of the major factors in determining their suitability for the use in the treatment and repair of bone and cartilage defects. For example, successful bone formation requires that these elements be combined in a well-coordinated spatial and time dependent fashion. Moreover, the relative contribution of each element may vary, e.g., according to differences in patient age, gender, health, systemic conditions, habits, anatomical location, etc.
Despite advances in the understanding in the treatment and repair of bone and cartilage defects, there is still a need for bioactive implants that are biocompatible, non-inflammatory, osteogenic, and chondrogenic, and can be replaced by a subject's natural bone and cartilage.